CO2 Elevation Accelerates Phenology and Alters Carbon/Nitrogen Metabolism vis-à-vis ROS Abundance in Bread Wheat.

Birendra K Padhan,Sandeep B Adavi,Viswanathan Chinnusamy,Lekshmy Sathee,Hari S Meena,Shailendra K Jha

doi:10.3389/fpls.2020.01061

Birendra K Padhan, Sandeep B Adavi + Show 4 more

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https://doi.org/10.3389/fpls.2020.01061

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Abstract

Wheat is an important staple food crop of the world and it accounts for 18–20% of human dietary protein. Recent reports suggest that CO2 elevation (CE) reduces grain protein and micronutrient content. In our earlier study, it was found that the enhanced production of nitric oxide (NO) and the concomitant decrease in transcript abundance as well as activity of nitrate reductase (NR) and high affinity nitrate transporters (HATS) resulted in CE-mediated decrease in N metabolites in wheat seedlings. In the current study, two bread wheat genotypes Gluyas Early and B.T. Schomburgk differing in nitrate uptake and assimilation properties were evaluated for their response to CE. To understand the impact of low (LN), optimal (ON) and high (HN) nitrogen supply on plant growth, phenology, N and C metabolism, ROS and RNS signaling and yield, plants were evaluated under short term (hydroponics experiment) and long term (pot experiment) CE. CE improved growth, altered N assimilation, C/N ratio, N use efficiency (NUE) in B.T. Schomburgk. In general, CE decreased shoot N concentration and grain protein concentration in wheat irrespective of N supply. CE accelerated phenology and resulted in early flowering of both the wheat genotypes. Plants grown under CE showed higher levels of nitrosothiol and ROS, mainly under optimal and high nitrogen supply. Photorespiratory ammonia assimilating genes were down regulated by CE, whereas, expression of nitrate transporter/NPF genes were differentially regulated between genotypes by CE under different N availability. The response to CE was dependent on N supply as well as genotype. Hence, N fertilizer recommendation needs to be revised based on these variables for improving plant responses to N fertilization under a future CE scenario.

Highlights

Atmospheric CO2 concentration is increasing exponentially and from the preindustrial level, it has increased by 40% and is expected to reach approximately 935 ppm by the end of 2100 (IPCC, 2014)
The average values of shoot biomass were highest for optimum nitrogen (ON) treatment in both CA (0.105 g) and CO2 elevation (CE) (0.117 g) treatments, whereas HN treatment resulted in reduction of shoot biomass in both CA (0.07 g) and CE (0.091 g) treatments
The average values of root biomass were highest for LN treatment in both CA (0.105 g) and CE (0.117 g) treatments, whereas HN treatment resulted in reduction of shoot biomass in both CA (0.024 g) and CE (0.028 g) treatments

Summary

Introduction

Atmospheric CO2 concentration is increasing exponentially and from the preindustrial level, it has increased by 40% and is expected to reach approximately 935 ppm by the end of 2100 (IPCC, 2014). Reports suggest that plants grown under CE have higher photosynthetic activity, higher nutrient uptake and increased productivity (Gruda et al, 2019). CO2 enrichment increases the biomass offood crops and tree crops (Luo et al, 2004; Lam et al, 2012) but lead to reduced food quality especially N constituents (Cotrufo et al, 1998; Taub and Wang, 2008). The lower N content of CE grown plants/food products has been credited to dilution effect of carbon accumulation (Taub and Wang, 2008), or low N availability (Rogers et al, 1998) or inhibition of shoot N assimilation (Bloom et al, 2002a; Bloom et al, 2002b) or decreased rate of transpiration (Myers et al, 2014). The reduced transpiration rates under CE indirectly inhibit N uptake and transport to leaves (Correia et al, 2005; Jauregui et al, 2016)

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